Growth Rates

Hi, I need to measure uptake / success of a program. This success is being evaluated based on transaction volumes.

Here's what I am thinking in terms of an approach. I'm not sure it's a good way to go. And I don't know for sure how to do the necessary calculations:

I have monthly transaction volume data from January 2011 to December 2011, inclusive. I am trying to figure out:

The annual growth rate
The monthly growth rate

I want the monthly growth rate because it (and the 2011 data) will be used as a baseline. The baseline will then be used to predict the volumes in 2012 and onward. The difference between the predicted volumes (based on the historical growth rate) and actual volumes will be the uptake and help evaluate effectiveness of a program.

I've found several sites on the web that provide answers but I don't feel confident in them. I don't think I want compound growth rate. Is that the same as Constant Growth Rate?

Re: Growth Rates

The formula to use for growth rate is change in volume divided by initial volume:

So the growth rate for a month would be: the volume for that month minus the volume for previous month divided by volume of the previous month. For example if cell A1 = volume for March and cell A2 = volume for April, then the April growth is (cellA2-cellA1)/cell A1. Similarly the growth rate for a year would be the volume for the year minus the volume for the previous year divided by the volume of previous year. You may want to convert these to a percentage.

Re: Growth Rates

thank you. The above formula will result in a different growth rate for each month. How can I find one number that would be applied to forecast the future? or would I have to apply the growth for a given month this year to the same month in 2012? Or do I use the annual growth rate and divide it by 12 to get one number for a forecast?